[0001] The present invention concerns a stereolithography method.
[0002] As is known, the stereolithography technique is used to produce three-dimensional
objects through the successive deposition of several layers of a light-sensitive liquid
resin capable of polymerizing through exposure to a light source.
[0003] In particular, each resin layer is superimposed to the preceding layer of the three-dimensional
object to be produced and is allowed to selectively solidify in the points corresponding
to the volume of the object itself.
[0004] A stereolithography machine according to a known embodiment comprises a container
suited to contain said liquid resin and provided with a transparent bottom.
[0005] There is also a light source, generally a laser emitter or a projector, capable of
selectively irradiating the layer of liquid resin arranged adjacent to the bottom
of the container so that it solidifies.
[0006] The machine comprises also a modelling plate suited to support the solidified layers
of the three-dimensional object, associated with actuator means suited to provide
for moving the plate in a direction perpendicular to the bottom of the container.
[0007] According to a stereolithography method of the known type using the above mentioned
machine, first of all the modelling plate is arranged at a distance from the bottom
of the container that is equal to the thickness of the layer to be solidified.
[0008] Successively, the liquid resin layer adjacent to the bottom of the container is selectively
irradiated by means of the light source in order to solidify it.
[0009] The modelling plate is configured so that the solidified layer adheres to it while,
in the contrary, the bottom of the container is provided with a covering that reduces
such adhesion.
[0010] The modelling plate is successively moved away from the bottom of the container,
so as to make the solidified layer emerge from the liquid resin and thus make it possible
to restore the thickness of the liquid resin that is necessary for processing a successive
layer of the object.
[0011] In fact, lifting the modelling plate and the solidified layer means leaving a depression
in the liquid resin, which is filled by the spontaneous flow of the resin itself.
[0012] Said levelling action restores the thickness of the liquid resin that is necessary
to solidify a new layer of the object and furthermore prevents air bubbles from remaining
trapped into the liquid resin during the successive lowering of the modelling plate,
which may affect the integrity of the successive layer of the three-dimensional object.
[0013] Once said spontaneous levelling is completed, the modelling plate is immersed again
in the liquid resin and a further layer of the object is solidified.
[0014] The method described above poses the drawback that the overall processing time of
the three-dimensional object is considerably prolonged due to the waiting time needed
after the solidification of each layer of the object for the liquid resin to level
out.
[0015] Since the number of layers that form an object obtained through stereolithography
can reach several hundreds, it can be understood that the waiting times mentioned
above result in a considerable increase in the processing time.
[0016] Obviously, the waiting times are proportional to the viscosity of the liquid resin.
Therefore, the drawback mentioned above is particularly important when resins of the
so-called "hybrid" type are used, which comprise particles in ceramic or other materials
mixed with the polymeric component.
[0017] Said hybrid resins are suitable for producing objects with high mechanical resistance
but on the other hand their viscosity is much higher compared to the other resins
commonly used in stereolithography.
[0018] A known embodiment, described in the Patent application
WO 2010/045950, includes a movable tank and a fixed levelling paddle arranged in contact with the
resin.
[0019] Before the solidification of each layer, the tank is moved so that the levelling
paddle fills the depression left by the modelling plate when it is lifted.
[0020] This embodiment poses the drawback that it requires a certain amount of space for
the movement of the tank that, consequently, involves an increase in the overall dimensions
of the machine.
[0021] Document
JP H07 1594 A discloses a method for producing a three-dimensional object according to the preamble
of claim 1.
[0022] The present invention intends to overcome all the drawbacks of the known art as outlined
above.
[0023] In particular, it is the object of the present invention to provide a stereolithography
method that makes it possible to produce a three-dimensional object through the solidification
of a fluid substance in layers, more rapidly than when employing the method of the
known type described above.
[0024] It is a further object of the invention to limit the overall dimensions of the machine
compared to the machines of the known type.
[0025] The above mentioned objects are achieved by a method for producing a three-dimensional
object in layers according to claim 1.
[0026] Further characteristics and details of the invention are described in the corresponding
dependent claims.
[0027] Advantageously, the method that is the subject of the invention makes it possible
to produce a three-dimensional object in an overall time that is substantially independent
of the viscosity of the fluid substance used.
[0028] Therefore, to advantage, the invention is particularly suited to be used with highly
viscous liquid substances like, for example, the hybrid resins mentioned above, or
with fluid pasty substances whose viscosity is even higher.
[0029] Still advantageously, the reduced overall dimensions make it easier to use the machine.
[0030] The said objects and advantages, together with others which will be highlighted below,
are illustrated in the description of some preferred embodiments of the invention
which are provided by way of non-limiting examples with reference to the attached
drawings, wherein:
- Figures from 1 to 6 show schematic side views of the stereolithography machine operating
according to the method of the invention, in different operating configurations.
[0031] The method of the invention is described with reference to a stereolithography machine
indicated as a whole by
1 in Figure 1, which comprises a container
2 containing a fluid substance
3 suited to be solidified through exposure to predefined radiation
4a.
[0032] It is specified since now that the term "fluid substance" means a substance suited
to be distributed in the container
2 so that its surfaces assumes a substantially flat shape, for example like that of
a liquid or pasty substance.
[0033] The fluid substance
3 is preferably but not necessarily a light-sensitive polymeric liquid resin and the
predefined radiation is light radiation.
[0034] In particular, said resin is of the so-called "hybrid" type, comprising particles
in ceramic or other materials that are capable of increasing the mechanical resistance
of the resin once it has solidified.
[0035] However, the method of the invention may be used with a fluid substance of any type,
provided that it is able to solidify following exposure to predefined radiation.
[0036] The machine
1 also comprises means
4 suited to emit the predefined radiation
4a, capable of selectively irradiating a layer of the fluid substance
3 having a predefined thickness and arranged adjacent to the bottom
2a of the container
2 so as to solidify it.
[0037] The emitter means
4 are preferably arranged under the container
2 and are configured so as to direct the predefined radiation
4a towards the bottom
2a of the container
2, which is transparent to radiation, as shown in Figure 2.
[0038] Preferably, if the fluid substance
3 is a light-sensitive resin, the emitter means
4 comprise a laser light emitter associated with means suited to direct the light beam
towards any point of the above mentioned layer of the fluid substance
3.
[0039] According to an exemplary embodiment of the invention, not illustrated herein, the
emitter means
4 comprise a projector suited to generate a luminous image corresponding to the surface
area of the layer of fluid substance
3 to be solidified.
[0040] The stereolithography machine
1 also comprises a modelling plate
5 facing the bottom
2a of the container
2 and suited to support the three-dimensional object
11 being formed.
[0041] The modelling plate
5 is associated with actuator means
7 suited to move it with respect to the bottom
2a according to a modelling direction
X that is perpendicular to the same bottom
2a.
[0042] In particular, the modelling plate
5 is configured in such a way that the fluid substance
3 adheres to it once it has solidified.
[0043] On the contrary, the bottom
2a of the container
2 is preferably made of a material that prevents said adhesion.
[0044] According to the method of the invention, the modelling plate
5 is immersed in the fluid substance
3 until arranging it at a distance from the bottom
2a that is equal to the thickness of the solidified layer to be obtained.
[0045] The layer of the fluid substance
3 is then selectively irradiated in order to obtain the solidified layer
6, which adheres to the modelling plate
5, as shown in Figures 2 and 3.
[0046] Successively, the modelling plate
5 is lifted in such a way as to move the solidified layer
6 away from the bottom
2a until it emerges from the fluid substance
3, as shown in Figure 4.
[0047] Following the above mentioned movement of the solidified layer
6 away from the bottom
2a, in the fluid substance
3 contained in the container
2 there still is a depressed area
3a at the level of the position previously occupied by the modelling plate
5 and/or by the three-dimensional object
11 being formed.
[0048] According to the method of the invention, to fill the above mentioned depression
3a, the fluid substance
3 is redistributed in the container
2 by pushing the fluid substance
3 towards the depression
3a through levelling means
8 arranged in contact with the fluid substance
3.
[0049] In particular, said levelling means
8 are associated with power means, not shown herein but known per se, configured so
as to move them with respect to the bottom
2a of the container
2 in contact with the fluid substance
3 according to a direction of movement
Y, so as to redistribute the fluid substance
3 as described above.
[0050] During said movement, the levelling means
8 are passed between the modelling plate
5 and the container
2, that is, under the modelling plate
5.
[0051] In this way, there is no need to move the container
2 to carry out the levelling operation and therefore it is possible to limit the overall
dimensions of the machine
1.
[0052] Successively, the modelling plate
5 is lowered again and the operations described above are repeated in order to obtain
the solidification of a further layer of the object
11.
[0053] It can be understood that the above mentioned levelling means
8 make it possible to fill the depression
3a in a much quicker way compared to the known method previously described, in which
the filling action is due to the spontaneous redistribution of the fluid substance.
[0054] Therefore, the waiting time for the levelling of the fluid substance
3 after the solidification of each layer of the object is considerably reduced, thus
reaching the aim to reduce the overall processing time compared to the time required
by the methods of the known type.
[0055] In particular, the higher the viscosity of the fluid substance
3 used, the shorter the overall processing time.
[0056] Therefore, the method of the invention is particularly suited to be used when the
fluid substance
3 is a hybrid resin with high viscosity, as previously explained.
[0057] Preferably, furthermore, to redistribute the fluid substance
3 during the interval between the solidification of two successive layers, the levelling
means
8 are moved in one direction only, opposite the direction corresponding to the previous
redistribution process, as can be seen in the figures.
[0058] In particular, once each layer has solidified, the levelling means
8 pass beyond the modelling plate
5 and come to be positioned beside the latter, on the opposite side with respect to
the side where they were positioned after the solidification of the previous layer.
[0059] In this way, to advantage, each operation for the redistribution of the fluid substance
3 does not require the return of the levelling means
8 to the initial position and is therefore particularly rapid.
[0060] The levelling means
8 are placed in contact with the surface of the fluid substance
3 in an area where the level is higher than the level of the fluid substance
3 at the height of the depression
3a, so as to be able to push the fluid substance
3 towards the depression
3a.
[0061] Preferably, the levelling means
8 comprise a paddle
9 mainly developed according to a longitudinal direction and whose length preferably
corresponds to the width of the container
2.
[0062] In the figures, the paddle
9 is shown in a side view and therefore the just mentioned longitudinal direction is
perpendicular to the plane of the figures themselves.
[0063] To push the fluid substance
3, the above mentioned paddle
9, arranged in contact with the fluid substance
3, is moved according to a direction of movement
Y that is perpendicular to the above mentioned longitudinal direction, as shown in
Figure 5.
[0064] The movement of the paddle
9 makes it possible to level the fluid substance
3 in such a way as to obtain a substantially uniform thickness, as shown in Figure
6.
[0065] Obviously, the paddle
9 can have any shape, even different from that shown in the figures, provided that
it is suited to come into contact with the surface of the fluid substance
3 contained in the container
2 in order to level it.
[0066] According to an exemplary embodiment of the invention not illustrated herein, the
container
2 is movable with respect to the modelling plate
5 in a direction
Y that is perpendicular to the longitudinal direction of the paddle
9.
[0067] In this case, the redistribution of the fluid substance
3 takes place through a combination of the movements of the paddle
9 and of the container
2.
[0068] The above clearly shows that the invention achieves all the set objects.
[0069] In particular, the use of levelling means to fill the depression present in the fluid
substance after the solidification of each layer of the object makes it possible to
reduce the waiting time before the solidification of the successive layer.
[0070] Consequently, the overall time necessary to make the three-dimensional object is
considerably reduced compared to the time needed when using the stereolithography
methods of the known type, and said time reduction becomes larger as the viscosity
of the fluid substance used increases.
[0071] Furthermore, the fact that the levelling means are moved so that they pass between
the modelling plate and the container makes it possible to limit the overall dimensions
of the machine.
[0072] The method that is the subject of the invention may be subjected to further changes
that, even though not described herein and not illustrated in the drawings, must all
be considered protected by the present patent, provided that they fall within the
scope of the following claims.
[0073] Where technical features mentioned in any claim are followed by reference signs,
those reference signs have been included for the sole purpose of increasing the intelligibility
of the claims and accordingly such reference signs do not have any limiting effect
on the protection of each element identified by way of example by such reference signs.
1. Method for producing a three-dimensional object (11) in layers by means of a stereolithography
machine (1) of the type comprising:
- a container (2) containing a fluid substance (3) in the liquid or paste state suited
to be solidified through exposure to predefined radiation (4a);
- means (4) for emitting said predefined radiation (4a), suited to selectively irradiate
a layer of said fluid substance (3) having a predefined thickness and arranged adjacent
to the bottom (2a) of said container (2) in order to solidify it;
- a modelling plate (5) suited to support said solidified layer (6);
- actuator means (7) suited to move said modelling plate (5) with respect to said
bottom (2a) at least according to a modelling direction (X) that is perpendicular
to said bottom (2a);
- levelling means (8) arranged in contact with said fluid substance (3);
said method comprising the following operations:
- selectively irradiating said layer of fluid substance (3) in such a way as to obtain
said solidified layer (6);
- moving said solidified layer (6) away from said bottom (2a) so as to make it emerge
from said fluid substance (3);
- redistributing said fluid substance (3) in said container (2) so as to fill the
depression (3a) caused by said movement of said solidified layer (6) away from said
bottom (2a),
characterized in that said modelling plate (5) or respectively said modelling plate and the solidified
layers is/are immersed in said fluid substance (3) until arranging said modelling
plate (5) or respectively the last solidified layer at a distance from said bottom
(2a) equal to said predefined thickness, and
in that said redistribution process takes place by moving said levelling means (8) between
said modelling plate (5) and said container (2) from a first area of said container
(2), in which the level of said fluid substance (3) is higher than the level of said
depression (3a), towards said depression (3a), wherein said levelling means (8) comprise
a paddle (9) developed mainly according to a longitudinal direction, said paddle (9)
having an edge facing said bottom (2a), wherein said edge is arranged inside said
container (2).
2. Method according to claim 1, characterized in that said edge is immersed in said fluid substance (3).
3. Method according to any preceding claims, characterized in that the depth of said fluid substance (3) is smaller than the depth of said container
(2).
4. Method according to any preceding claims, characterized in that said movement is performed through the displacement of said paddle (9) in a direction
of movement (Y) perpendicular to said longitudinal direction.
5. Method according to any of the preceding claims, characterized in that during each redistribution process of said fluid substance (3) that takes place during
the interval between the solidification of two successive layers said movement takes
place in a single direction of movement (Y) so that said paddle (9) passes from one
side of said modelling plate (5) to the other.
6. Method according to claim 5), characterized in that said movement of said paddle (9) during each of said redistribution operations takes
place in the opposite direction with respect to the previous redistribution operation.
7. Method according to any claim from 1) to 6), characterized in that said fluid substance (3) is a mixture comprising a polymeric component and a particulate
material, or is a pasty substance.
8. Method according to any preceding claims, characterized in that said movement of said paddle (9) is made by power means configured so as to move
said paddle (9) perpendicular to said bottom (2a) and to immerse it in and extract
it from said fluid substance (3).
9. Method according to claim 8), characterized in that said paddle (9) is configured such that said movement of said paddle (9) is capable
of conferring a uniform thickness to said fluid substance (3).
10. Method according to claim 9), characterized in that said paddle (9) is arranged at a distance from said bottom (2a).